BRUSSELS—The International Monetary Fund is expected to announce Thursday a tentative bailout deal of around $15 billion for Ukraine as part of a broader international aid package, people familiar with the negotiations said.

The agreement, now in the final stages of negotiation between IMF staff and top Ukrainian officials, still would need formal approval by the fund's board in Washington. It would require the government in Kiev to overhaul a number of economic policies, including politically sensitive measures that must...